The stagnant water in plumbing systems can lead to a buildup of harmful bacteria if not properly managed by facilities managers, according to a report in the New York Times. Particularly worrisome is Legionella bacteria, which can cause Legionnaires’ disease, a serious type of pneumonia, according to the Centers for Disease Control and Prevention (CDC).

Those at greater risk include people with weakened immune systems, current or former smokers, and those over 50 years old, among other precursors, according to the CDC.

After the bacteria multiplies in a building’s water system, people can breathe in water droplets containing Legionella. Though less common, people can also get sick if, while drinking water containing Legionella, water accidentally goes into the lungs, the CDC notes. In 2018, health departments reported almost 10,000 cases of Legionnaires’ disease in the U.S.

One challenge facing property managers in addressing water safety may be “incomplete and inconsistent guidance from regulators and health authorities,” according to the report. A study out of Purdue University on water quality in shutdown buildings says “health officials, building owners, utilities and other entities are rapidly developing guidance” for the potential safety issues.

“Not all of the guidelines are created equal,” Caitlin Proctor, a postdoctoral fellow at Purdue who helped conduct the study, told the newspaper. “The original CDC guidelines only covered certain systems.”

Proctor said coronavirus patients and survivors could be more vulnerable to the disease.